1. Field of the Invention
The invention is concerned with copper based alloys.
2. Description of the Prior Art
Alloys containing copper, nickel, and tin have been proposed as economical substitutes for copper-beryllium and phosphor-bronze alloys in the manufacture of shaped articles such as wire, wire connectors, springs, and relay elements. Among alloy properties on which such use is based are high strength, good formability, corrosion resistance, solderability, and electrical conductivity. Cu-Ni-Sn alloys exhibiting desirable combinations of properties are disclosed in U.S. Pat. No. 3,937,638, U.S. Pat. No. 4,052,204, and U.S. Pat. No. 4,090,890, all in the name of J. T. Plewes.
U.S. Pat. No. 3,937,638 discloses a treatment of a Cu-Ni-Sn cast ingot which involves homogenizing, cold working, and aging and which leads to a predominantly spinodal structure in the treated alloy. For example, in the case of an alloy containing seven percent Ni, eight percent Sn, and remainder copper, an exemplary method calls for homogenizing the cast ingot, cold working to achieve 99 percent area reduction, and aging for eight seconds at a temperature of 425 degrees C. The resulting article has 0.01 percent yield strength of 173,000 psi and ductility of 47 percent area reduction to fracture.
U.S. Pat. No. 4,052,204 discloses quaternary alloys containing not only Cu, Ni, and Sn, but also at least one additional element selected from among the elements Fe, Zn, Mn, Zr, Nb, Cr, Al, and Mg. A predominantly spinodal structure is produced in these alloys by a treatment of homogenizing, cold working, and aging analogous to the treatment disclosed in U.S. Pat. No. 3,937,638.
U.S. Pat. No. 4,090,890, discloses cold rolled and aged strip material made of alloys having a composition similar to the composition of alloys disclosed in U.S. Pat. No. 3,937,638 and U.S. Pat. No. 4,052,204 and having not only high strength, but also essentially isotropic formability. As a consequence, such strip material is particularly suited for the manufacture of articles which require bending of the strip in directions having a substantial component perpendicular to the rolling direction.
Cu-Ni-Sn alloys and their properties are a subject also of the following papers: L. H. Schwartz, S. Mahajan, and J. T. Plewes, "Spinodal Decomposition in a Cu-9 wt% Ni-6 Sn Alloy", Acta Metallurgica, Vol. 22, May 1974, pp. 601-609; L. H. Schwartz and J. T. Plewes, "Spinodal Decomposition in Cu-9wt% Ni-6wt% Sn-II. A Critical Examination of Mechanical Strength of Spinodal Alloys", Acta Metallurgica, Vol. 22, July 1974, pp. 911-921; John T. Plewes, "Spinodal Cu-Ni-Sn alloys are Strong and Superductile", Metal Progress, July 1974, pp. 46-50; J. T. Plewes, "High-Strength Cu-Ni-Sn alloys by Thermomechanical Processing", Metallurgical Transactions A, Vol. 6A, March 1975, pp. 537-544.
The achievement of good strength and bend properties in copper based alloys containing Ni and Sn is an object also of the method disclosed in U.S. Pat. No. 3,941,620, M. J. Pryor et al., "Method of Processing Copper Base Alloys". Pryor discloses a method for treating an ingot by homogenizing, cold rolling, aging, and again cold rolling.